Selective sputtering for pattern transfer

ABSTRACT

Methods of patterning conductive layer with a mask are described. The methods include low-ion-mass sputtering of the conductive layer by accelerating (e.g. helium or hydrogen containing ions) toward a substrate which includes the patterned mask and the underlying conductive layer. The sputtering processes described herein selectively remove conductive layers while retaining mask material.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Prov. Pat. App. No. 61/845,444 filed Jul. 12, 2013, and titled “SELECTIVE SPUTTERING FOR PATTERN TRANSFER” by Hoinkis et al., which is hereby incorporated herein in its entirety by reference for all purposes.

FIELD

The present invention relates to selective sputtering processes.

BACKGROUND

The use of copper as a conductive interconnect material is favored in semiconductor devices because of the high conductivities and circuit speeds copper enables. On the other hand, copper is difficult to pattern and copper interconnect leads have predominantly been formed using damascene and dual damascene processing technology. In damascene processing sequences, openings are formed in a dielectric layer on a substrate such as a semiconductor substrate used to form semiconductor devices. Copper is deposited over the dielectric layer and within the openings. Polishing/planarization removes copper from over the dielectric leaving the copper inlaid within the openings. In this way, the burden on photolithography is shifted from copper to the more manageable dielectric layer. The inlaid copper includes an upper surface that is essentially co-planar with the top surface of the patterned dielectric layer in which the copper is formed.

Subtractive copper etching is the alternative to a damascene process flow. A layer of copper is deposited and then patterned to form horizontal electrical interconnections. Early attempts to investigate subtractive copper etching used plasma excited halides which were found to provide many advantages but degraded the physical integrity of the copper near grain boundaries and other seams. Thus, there is a need in the art to develop alternatives to halide-based chemical etch processes for subtractive etching of copper layers.

SUMMARY

This invention involves the selective removal of materials which do not form volatile etch byproducts at low temperatures. Many of these materials are metals and are conductive, so the term “conductive layer” may be used herein the describe the layer to be patterned. A small subset of materials may simply contain metallic elements (e.g. MgO) which will still be called conductive layers since they become conductive under the sputtering conditions described herein. As such, “conductive layer” is functionally synonymous with “materials which do not form volatile etch byproducts.” Methods of patterning a conductive layer with a mask are described. The methods include low-ion-mass sputtering of the conductive layer by accelerating (e.g. helium or hydrogen containing ions) toward a substrate which includes the patterned mask and the underlying conductive layer. The sputtering processes described herein selectively remove conductive layers while retaining mask material.

Embodiments of the invention include a method of patterning a conductive layer. The method includes transferring a substrate into a substrate processing region of a substrate processing chamber. The portion of the substrate is the conductive layer. The method further includes flowing a sputtering gas into a sputtering generation region fluidly coupled to the substrate processing region while forming a sputtering plasma in the sputtering generation region. The sputtering plasma is formed by applying a sputtering plasma power to form ions. The method further includes selectively removing portions of the conductive layer which are not covered by a patterned mask layer by bombarding exposed portions of the conductive layer with the ions accelerated towards the substrate with an accelerating potential. The substrate is in the substrate processing region during the selective removal operation.

Embodiments of the invention include method of patterning a conductive layer. The method includes providing a patterned substrate having a conductive layer a patterned mask layer formed on the conductive layer. The patterned substrate is in a substrate processing region of a substrate processing chamber. the method further includes flowing a sputtering gas into a sputtering generation region fluidly coupled to the substrate processing region while forming a sputtering plasma in the sputtering generation chamber. The sputtering plasma is formed by applying a sputtering plasma power to form sputtering ions and the sputtering generation region consists essentially of elements with atomic weights below ten atomic mass units. The method further includes selectively removing portions of the conductive layer which are not covered by the patterned mask layer by bombarding exposed portions of the conductive layer with the sputtering ions accelerated towards the substrate with an accelerating potential. The substrate is in the substrate processing region during the selective removal operation.

Embodiments of the invention include methods of patterning a copper layer. The method includes flowing a sputtering gas into a sputtering generation region of the substrate processing chamber while forming a sputtering plasma in the substrate processing chamber. The sputtering plasma is formed by applying a sputtering plasma power to form sputtering ions. The sputtering gas consists essentially of one or more of atomic hydrogen (H), hydrogen (H₂) and helium. The method further includes selectively removing portions of the copper layer which are not covered by a patterned mask layer formed on the conductive layer by bombarding exposed portions of the conductive layer with sputtering ions accelerated towards the substrate with an accelerating potential. The patterned mask layer comprises tungsten or tantalum.

Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the disclosed embodiments. The features and advantages of the disclosed embodiments may be realized and attained by means of the instrumentalities, combinations, and methods described in the specification.

DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the embodiments may be realized by reference to the remaining portions of the specification and the drawings.

FIG. 1 is a flow chart of a sputter-based pattern transfer process according to embodiments.

FIG. 2 is a schematic of a substrate processing chamber which can be used to carry out sputter-based pattern transfer processes according to embodiments.

FIG. 3 is a schematic diagram of a substrate processing chamber according to embodiments.

FIG. 4 is a schematic top-view diagram of an illustrative multi-chamber processing system according to embodiments.

In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

DETAILED DESCRIPTION

Methods of patterning a conductive layer with a mask are described. The methods include low-ion-mass sputtering of the conductive layer by accelerating (e.g. helium or hydrogen containing ions) toward a substrate which includes the patterned mask and the underlying conductive layer. The sputtering processes described herein selectively remove conductive layers while retaining mask material.

Etch processes typically use plasma-excited reactants and formation of volatile product(s) to selectively remove one material while leaving another (for example, a mask) intact. Volatile products leave the surface of the etched material due to the reduced desorption energy of the volatile products. However, there exist many materials (e.g. Cu, Fe, and MgO) which have few or no such volatile products that form at low substrate temperatures. Transferring a pattern into a blanket layer of such materials can be difficult or impossible using conventional etch processes. The embodiments described herein enable pattern-transfer process for materials which form no volatile products. The embodiments provide the further advantage of being highly selective of conductive blanket layers. For example, copper removal may be patterned by physical sputtering rather than by formation of volatile organo-Cu-complexes. In view of the supposed mechanism, the terms “removal” and “removing” will often be used herein in place of “etching”. The Cu-to-Ta removal selectivity ratio markedly increased as the ion-atomic weight was decreased and as the ion energy was decreased.

In order to better understand and appreciate the invention, reference is now made to FIG. 1 which is a flow chart of an exemplary sputter-based pattern transfer process 100 according to embodiments. Reference will concurrently be made to FIG. 2 which shows a schematic of an exemplary substrate processing chamber which may be used to perform exemplary sputter-based pattern transfer processes. A wide variety of substrate processing chambers may also be used to perform claimed sputter-based pattern transfer process 100 described herein. The exemplary substrate 206 is coated with a blanket layer of copper and a mask layer is formed and patterned atop the copper layer. The substrate is then transferred into the substrate processing region of a substrate processing chamber (operation 110). A sputtering plasma is formed from helium or another sputtering gas having mass less than ten atomic mass units (operation 120). The helium or other sputtering gas may be flowed into the sputtering generation region before and/or during the application of the RF power to form the sputtering plasma. The copper layer is removed (operation 130) by sputtering to transfer the pattern of the mask into the copper and removal byproducts are either pumped out of the substrate processing region through vacuum pump 202 or “plate out” on the interior surfaces of the substrate processing chamber.

During the pattern transfer process, the sputtering gas is delivered through gas inlets 250 into sputtering generation region 210. The sputtering gas is excited in an inductively-coupled plasma created by applying inductively-coupled power in the form of alternating current (AC) power 241 to inductive coils 240. The plasma will be referred to herein as a sputtering plasma and is applied with a sputtering plasma power. Electromagnetic radiation passes through dielectric window 220 to ignite a plasma in sputtering generation region 210 from the sputtering gas. Dielectric window 220 mates with bottom chamber portion 200 to form the bulk of the substrate processing chamber. The sputtering gas may be described as inert, which indicates that the elements of the sputtering gas do not form chemical bonds with removed constituents of the conductive layer. This mechanism contrasts with more canonical etch processes which form volatile species made from material from the etchant and the etched material. Neither the sputtering gas nor the sputtering ions form chemical bonds with the conductive layer or removed constituents of the conductive layer.

Using low mass sputtering gases increases the removal selectivity of target materials as described herein. The sputtering gas may have a mass below or about ten atomic mass units (amus) or below or about six atomic mass units, in embodiments. The sputtering generation region (or the sputtering gas) may comprise at least one of helium and hydrogen (H₂), may consist essentially of hydrogen, may consist essentially of helium, may consist essentially of one or both of hydrogen and helium, may consist essentially of one or more of atomic hydrogen (H), hydrogen (H₂) and helium, may consist essentially of elements with atomic mass less than ten atomic mass units, or may consist essentially of elements with atomic mass less than six atomic mass units according to embodiments. Sputtering plasma excited species (sputtering ions or simply ions) formed from sputtering gases remove exposed copper from substrate 206 in regions which are not covered by mask material. Sputtering generation region 210 and/or substrate processing region 211 may be essentially devoid of any molecules having mass greater than six or ten atomic mass units in embodiments. The sputtering gas (e.g. helium) may be supplied to sputtering generation region 210 at a flow rate of between about 50 sccm (standard cubic centimeters per minute) and 2 slm according to embodiments.

The RF frequency applied to form the sputtering plasmas described herein may be low RF frequencies less than about 200 kHz, high RF frequencies between about 10 MHz and about 15 MHz, or microwave frequencies greater than or about 1 GHz in embodiments. Generally speaking lower frequency ranges such as: less than 200 kHz, less than 500 kHz or less than 1 MHz may be used for bias purposes (when AC power is used) and for capacitively coupled plasma (which inherently accelerates ions toward the surface).

Plasma-excitation of the sputtering gas forms sputtering ions which are accelerated toward substrate 206 by applying an accelerating electrical potential (e.g. AC power 261) to conductive lid 260 relative to substrate pedestal 205 which determines the nearly identical potential of substrate 206 in this example. The accelerating potential may be alternating current (AC), direct current (DC) or a combination of the two. Decreasing the magnitude of the accelerating potential increases selectivity of the conductive blanket layer (the target layer) relative to the mask layer while decreasing the removal rate of the conductive blanket layer somewhat. The accelerating potential applied may result in between 500 eV and 1000 eV kinetic energy of the sputtering ions upon impact with the substrate. In another embodiment, the kinetic energy may be greater than 300 eV, greater than 500 eV, lesser than 4 keV, or lesser than 10 keV in embodiments. Any of the upper bounds may be combined with any of the lower bounds to form additional embodiments. As indicated previously, reducing the atomic masses of the sputtering ions has an effect similar to decreasing the accelerating potential, namely the selectivity improves at the expense of absolute removal rate.

With this in mind, maintaining some spatial separation between sputtering generation region 210 and substrate processing region 211 reduces an instance of excitation of removed constituents of the conductive layer in the sputtering plasma. If constituents sputtered from the conductive layer find their way into the sputtering plasma, undesirable self-sputtering may occur which would reduce selectivity by increasing the mass of some sputtering ions. The sputtering ions may include one or more of He+, H+, H₂+ and H₃+, which increase the selectivity of the conductive layer relative to heavier atomic mass unit alternatives.

In FIG. 2, sputtering generation region 210 is shown physically separate from substrate processing region 211 but still within the substrate processing chamber. Variations from this architecture are also possible and within the scope of this disclosure. Sputtering generation region 210 and substrate processing region 211 may overlap or completely coincide despite a potential reduction in removal selectivity of conductive layer material relative to patterned mask layer material. According to embodiments, the only elemental components within the substrate processing chamber during the sputtering process having mass greater than six or ten amu are sputtered components of the substrate itself In this case the removal selectivity is maintained as high as possible despite the use of a simplified processing chamber.

As shown in FIG. 2, the substrate processing region is a region within the substrate processing chamber and the sputtering generation region may also be a region within the substrate processing chamber. On the other hand, sputtering generation region 210 may be in a separate region remote from the substrate processing chamber shown in FIG. 2. A remote sputtering generation region may even be pumped by a separate pumping pathway to further reduce any potential self-sputtering activity and purify the sputtering ions to include only low mass components as described herein. Stated another way. the sputtering generation region may be in a separate compartment which is differentially pumped relative to the substrate processing region yet fluidly coupled to the substrate processing region.

The substrate processing region, the sputtering generation region and/or the substrate processing chamber may contain only inert gases, associated ions and desorbed species during operations 120-130 in embodiments. Operation 130 selectively removes copper from the substrate and may do so without removing significant amounts of the mask material from atop the copper layer according to embodiments. Generally speaking, the copper layer may be any conductive blanket layer underlying a patterned mask layer. The removal selectivity is quantified as a linear removal rate, for example, as a linear thinning of a blanket layer. The removal selectivity of the conductive blanket layer relative to the mask layer may be greater than 50:1, greater than 100:1, greater than 150:1 or greater than 200:1 in embodiments. Removal selectivities described herein may be achieved at relatively low substrate temperatures. The temperature of the substrate may be between about −20° C. and about 200° C. during any or all selective removal processes described herein.

Regarding the particular example of FIG. 1, the conductive blanket layer may comprise or consist essentially of copper. The patterned mask layer may comprise at least one of tantalum and tungsten or may consist essentially of one or both of tantalum and tungsten in embodiments. More generally, the conductive blanket layer may comprise or consist essentially of at least one of copper, iron, cobalt, magnesium, palladium, aluminum or platinum. The patterned mask layer may comprise or consist essentially of tantalum or tungsten, or their oxides or nitrides: tantalum oxide, tantalum nitride, tungsten oxide or tungsten nitride, according to embodiments. The patterned mask layer may comprise or consist essentially of osmium, rhenium, or their oxides or nitrides analogous to the tantalum and tungsten examples. In embodiments, the atomic mass of the primary constituent of the conductive blanket layer may be less than 30 amu, less than 35 amu, less than 40 amu or less than 45 amu. The atomic mass of the primary constituent (not oxygen or nitrogen in this case) of the patterned mask layer may have an atomic mass greater than greater than 45 amu, greater than 50 amu, greater than 55 amu or greater than 60 amu in embodiments. These demarcation points are not universally true, but separate many of the materials which have industrial relevance and satisfy the selectivity relationships outlined herein. A complementary demarcation method (similarly not universal) involves a comparison of melting points which offers another portal into the cohesiveness of a material and the associated ability to withstand or succumb to sputtering. The melting point of the mask material may be greater than 2000° C., greater than 2400° C. or greater than 2800° C. according to embodiments. At the same time, the conductive layer may have a melting point less than 3000° C., less than 2600° C. or less than 2200° C. in embodiments.

Consisting “essentially” of a material, as recited occasionally herein, means that a material, gas or precursor may include unavoidable concentrations of “impurities” or small concentrations which are consciously tolerated but do not significantly alter the primary function of the recited material. For example, copper having tolerated impurities would still possess a desirably high conductivity.

The method includes applying energy to the sputtering gas in first local plasma and to the inert gas (e.g. helium) in the second local plasma while in the substrate processing region to generate the radicals used to treat and etch the interior surfaces of the substrate processing chamber. The sputtering plasma may be generated using known techniques (e.g., radio frequency excitations, capacitively-coupled power and/or inductively coupled power). In an embodiment, the energy is applied using plasma power supply unit 241. The AC power is supplied to the inductive coils 240 shown in cross-section in FIG. 2. The AC bias power is supplied with auxiliary power supply unit 261. The sputtering plasma power may be between about 100 watts and about 5000 watts, between about 200 watts and about 4000 watts, between about 300 watts and about 3000 watts, or between about 500 watts and about 2000 watts in embodiments. In embodiments, an AC or DC (or AC+DC) accelerating voltage may be applied between substrate pedestal 205 and conductive lid 260 to accelerate ions and selectively remove exposed target materials from the substrate 206. The pressure within the substrate processing chamber may be between about 0.3 mTorr and about 1 Torr, between about 1 mTorr and about 300 mTorr or between about 3 mTorr and about 200 mTorr, according to embodiments, during operations 120 and/or operation 130.

Additional considerations will be presented in the course of presenting an alternative exemplary substrate processing chamber as well as an exemplary substrate processing system which may be used to perform sputter-based pattern transfer process 100.

Exemplary Processing Equipment

FIG. 3 depicts a schematic diagram of an substrate processing chamber 1001 which can be incorporated into a substrate processing system 1101 described later with reference to FIG. 4. Exemplary substrate processing chamber 1001 may also be referred to as a decoupled-plasma source chamber or DPS chamber. Substrate processing chamber 1001 includes inductive coils 1012, positioned exterior to a dielectric, dome-shaped ceiling 1020 (referred to herein as the dome 1020). Other chambers may have other types of ceilings, e.g., a flat ceiling. Inductive coil 1012 can be coupled to a radio-frequency (RF) source 1018 (that is generally capable of producing an RF signal having a tunable frequency). RF source 1018 is coupled to inductive coil 1012 through a matching network 1019. Substrate processing chamber 1001 can include a substrate support pedestal (cathode) 1016 that is coupled to a second RF source 1022 that is generally capable of producing an RF signal. RF source 1022 can be coupled to pedestal 1016 through a matching network 1024. Substrate processing chamber 1001 may also contain a conductive chamber wall 1030 that is connected to an electrical ground 1034. A controller 1040 including a central processing unit (CPU) 1044, a memory 1042, and support circuits 1046 for a CPU 1044 is coupled to various components of substrate processing chamber 1001 to facilitate control of the etch process.

In operation, a semiconductor substrate 1014 is placed on pedestal 1016 and gases are supplied from gas handling system 1038 to substrate processing chamber 1001 through entry port(s) 1026 into sputtering generation region 1050. A sputtering plasma is ignited in sputtering generation region 1050 in substrate processing chamber 1001 by applying RF power from RF sources 1018 and 1022 respectively to inductive coil 1012 and pedestal 1016. Ions are accelerated using RF source 1022 toward substrate 1014 which is located in substrate processing region 1052. The pressure within the interior of substrate processing chamber 1001 is controlled using a throttle valve 1027 situated between substrate processing chamber 1001 and a vacuum pump 1036. The temperature at the surface of chamber wall 1030 is controlled using liquid-containing conduits (not shown) that are located in chamber wall 1030 of substrate processing chamber 1001.

The temperature of substrate 1014 is controlled by stabilizing the temperature of pedestal 1016 and flowing helium gas from a helium source 1048 to channels formed by the back of substrate 1014 and grooves (not shown) on the pedestal surface. The helium gas is used to facilitate heat transfer between pedestal 1016 and substrate 1014. During the etch process, substrate 1014 is heated by a resistive heater within the pedestal to a steady state temperature and the helium facilitates uniform heating of substrate 1014. Using thermal control of both dome 1020 and pedestal 1016, substrate 1014 is maintained at a temperature of between about 100° C. and about 500° C.

FIG. 4 is a schematic top-view diagram of an illustrative multi-chamber processing system 1101. The processing system 1101 can include one or more load lock chambers 1102, 1104 for transferring of substrates into and out of the processing system 1101. Typically, since the processing system 1101 is under vacuum, the load lock chambers 1102, 1104 may “pump down” the substrates introduced into the processing system 1101. A first robot 1110 may transfer the substrates between the load lock chambers 1102, 1104, and a first set of one or more substrate processing chambers 1112, 1114, 1116, 1118 (four are shown). Each processing chamber 1112, 1114, 1116, 1118, can be outfitted to perform a number of substrate processing operations including the dry etch processes described herein in addition to cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, degas, orientation and other substrate processes.

The first robot 1110 can also transfer substrates to/from one or more transfer chambers 1122, 1124. The transfer chambers 1122, 1124 can be used to maintain ultrahigh vacuum conditions while allowing substrates to be transferred within the processing system 1101. A second robot 1130 can transfer the substrates between the transfer chambers 1122, 1124 and a second set of one or more processing chambers 1132, 1134, 1136, 1138. Similar to processing chambers 1112, 1114, 1116, 1118, the processing chambers 1132, 1134, 1136, 1138 can be outfitted to perform a variety of substrate processing operations including the dry etch processes described herein in addition to cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, degas, and orientation, for example. Any of the substrate processing chambers 1112, 1114, 1116, 1118, 1132, 1134, 1136, 1138 may be removed from the processing system 1101 if not necessary for a particular process to be performed by the processing system 1101. A copper etch processing chamber for carrying out the methods described and claimed herein may be installed in any one or more of substrate processing chamber locations.

System controller 1157 is used to control motors, valves, flow controllers, power supplies and other functions required to carry out process recipes described herein. System controller 1157 may rely on feedback from optical sensors to determine and adjust the position of movable mechanical assemblies. Mechanical assemblies may include the robot, throttle valves and susceptors which are moved by motors under the control of system controller 1157. A gas handling system 1155 is used to deliver halogen-containing precursors and inert species at various stages during the methods described herein.

In an exemplary embodiment, system controller 1157 includes a hard disk drive (memory), USB ports, a floppy disk drive and a processor. System controller 1157 includes analog and digital input/output boards, interface boards and stepper motor controller boards. Various parts of multi-chamber processing system 1101 which contains processing chamber 400 are controlled by system controller 1157. The system controller executes system control software in the form of a computer program stored on computer-readable medium such as a hard disk, a floppy disk or a flash memory thumb drive. Other types of memory can also be used. The computer program includes sets of instructions that dictate the timing, mixture of gases, chamber pressure, chamber temperature, RF power levels, susceptor position, and other parameters of a particular process.

A process for patterning, forming or otherwise processing a film on a substrate or a process for cleaning chamber can be implemented using a computer program product that is executed by the controller. The computer program code can be written in any conventional computer readable programming language: for example, 68000 assembly language, C, C++, Pascal, Fortran or others. Suitable program code is entered into a single file, or multiple files, using a conventional text editor, and stored or embodied in a computer usable medium, such as a memory system of the computer. If the entered code text is in a high level language, the code is compiled, and the resultant compiler code is then linked with an object code of precompiled Microsoft Windows® library routines. To execute the linked, compiled object code the system user invokes the object code, causing the computer system to load the code in memory. The CPU then reads and executes the code to perform the tasks identified in the program.

The interface between a user and the controller may be via a touch-sensitive monitor and may also include a mouse and keyboard. In one embodiment two monitors are used, one mounted in the clean room wall for the operators and the other behind the wall for the service technicians. The two monitors may simultaneously display the same information, in which case only one is configured to accept input at a time. To select a particular screen or function, the operator touches a designated area on the display screen with a finger or the mouse. The touched area changes its highlighted color, or a new menu or screen is displayed, confirming the operator's selection.

Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosed embodiments. Additionally, a number of well known processes and elements have not been described to avoid unnecessarily obscuring the present invention. Accordingly, the above description should not be taken as limiting the scope of the invention.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a process” includes a plurality of such processes and reference to “the dielectric material” includes reference to one or more dielectric materials and equivalents thereof known to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and “includes” when used in this specification and in the following claims are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, acts, or groups. 

The invention claimed is:
 1. A method of patterning a conductive layer, the method comprising: transferring a substrate into a substrate processing region of a substrate processing chamber, wherein a portion of the substrate is the conductive layer; flowing a sputtering gas into a sputtering generation region fluidly coupled to the substrate processing region while forming a sputtering plasma in the sputtering generation region, wherein the sputtering plasma is formed by applying a sputtering plasma power to form ions; selectively removing portions of the conductive layer which are not covered by a patterned mask layer by bombarding exposed portions of the conductive layer with the ions accelerated towards the substrate with an accelerating potential, wherein the substrate is in the substrate processing region during the selective removal operation, wherein the sputtering generation region and the substrate processing region are devoid of molecules having mass greater than ten atomic mass units.
 2. The method of claim 1 wherein the conductive layer comprises copper.
 3. The method of claim 1 wherein the conductive layer consists essentially of copper.
 4. The method of claim 1 wherein the conductive layer comprises at least one of iron, cobalt, magnesium, palladium, aluminum or platinum.
 5. The method of claim 1 wherein the patterned mask layer comprises at least one of tantalum and tungsten.
 6. The method of claim 1 wherein the patterned mask layer consists essentially of one or both of tantalum and tungsten.
 7. The method of claim 1 wherein the patterned mask layer comprises at least one of tantalum oxide, tantalum nitride, tungsten oxide, tungsten nitride, rhenium or osmium.
 8. The method of claim 1 wherein the sputtering generation region is in a separate compartment from the substrate processing region, wherein the sputtering generation region is differentially pumped relative to the substrate processing region yet fluidly coupled to the substrate processing region.
 9. The method of claim 1 wherein the sputtering generation region is inside the substrate processing chamber.
 10. The method of claim 1 wherein the sputtering plasma is attained by applying inductively-coupled power to the sputtering generation region.
 11. The method of claim 1 wherein neither the sputtering gas nor the sputtering ions form chemical bonds with removed constituents of the conductive layer.
 12. A method of patterning a conductive layer, the method comprising: providing a patterned substrate having a conductive layer a patterned mask layer formed on the conductive layer, wherein the patterned substrate is in a substrate processing region of a substrate processing chamber; flowing a sputtering gas into a sputtering generation region fluidly coupled to the substrate processing region while forming a sputtering plasma in the sputtering generation region, wherein the sputtering plasma is formed by applying a sputtering plasma power to form sputtering ions and wherein the sputtering generation region and the substrate processing region consist essentially of elements with atomic weights below ten atomic mass units; selectively removing portions of the conductive layer which are not covered by the patterned mask layer by bombarding exposed portions of the conductive layer with the sputtering ions accelerated towards the substrate with an accelerating potential, wherein the substrate is in the substrate processing region during the selective removal operation.
 13. The method of claim 12 wherein the sputtering generation region and the substrate processing region consist essentially of elements with atomic weights below six atomic mass units.
 14. The method of claim 12 wherein the sputtering gas comprises at least one of helium and hydrogen (H₂).
 15. A method of patterning a copper layer, the method comprising: flowing a sputtering gas into a sputtering generation region of the substrate processing chamber while forming a sputtering plasma in the substrate processing chamber, wherein the sputtering plasma is formed by applying a sputtering plasma power to form sputtering ions, wherein the sputtering gas consists essentially of one or more of atomic hydrogen (H), hydrogen (H_(z)) and helium; selectively removing portions of the copper layer which are not covered by a patterned mask layer formed on the conductive layer by bombarding exposed portions of the conductive layer with sputtering ions accelerated towards the substrate with an accelerating potential, wherein the patterned mask layer comprises tungsten or tantalum and wherein the sputtering generation region and the substrate processing region are devoid of molecules having mass greater than ten atomic mass units. 